It was the edge of the Wilkins Ice Shelf and has been there for hundreds, maybe 1,500 years.

This is the result of global warming, said British Antarctic Survey scientist David Vaughan.

Because scientists noticed satellite images within hours, they diverted satellite cameras and even flew an airplane over the ongoing collapse for rare pictures and video.

"It's an event we don't get to see very often," said Ted Scambos, lead scientist at the National Snow and Ice Data Center in Boulder, Colorado.

"The cracks fill with water and slice off and topple. That gets to be a runaway situation."

Global Warming

While icebergs naturally break away from the mainland, collapses like this are unusual but are happening more frequently in recent decades, Vaughan said. (Related: National Geographic's Larsen Ice Shelf Expedition.)

The collapse is similar to what happens to hardened glass when it is smashed with a hammer, he said.

The rest of the Wilkins Ice Shelf, which is about the size of Connecticut, is holding on by a narrow beam of thin ice.

Scientists worry that it too may collapse. Larger, more dramatic ice collapses occurred in 2002 and 1995.